The method of electro-photographic printing is well known in the art. In this method, a photoconductive surface, typically on a drum, is charged to a uniform potential. The charged photoreceptor and/or photoconductive surface are exposed to a light image from, for example, a writing head laser that discharges specific areas on the photoconductive surface. This records an electrostatic latent image on the photoconductive surface. After the photoconductive image is recorded, the latent image is developed with liquid toner. The developed image is transferred to an intermediate transfer member (ITM) such as a blanket and subsequently transferred to a substrate, such as paper. The ITM is typically heated to improve transferability of the developed image.
Between prints, a cleaning station applies a cleaning liquid, e.g. imaging oil, on a developer surface, e.g. the photoconductive surface to pickup any residual material, e.g. toner and/or surface material left on the surface. The cleaning liquid is also used to cool the developer surface. The cleaning liquid is subsequently removed together with any residual material collected and returned to a reservoir where the liquid is stored. The cleaning liquid is recirculated using a filtration system that pumps liquid from the reservoir, through one or more filters and a heat exchanger, and returns the filtered and cooled cleaning liquid back to the reservoir. The heat exchanger serves to maintain the cleaning liquid in the reservoir at a working temperature suitable for cleaning the developed surfaces. Typically, cleaning liquid is supplied to the cleaning station through an intersection between the cleaning station pump outlet and the filters so that the temperature and quality of the cleaning liquid supplied to the cleaning station is the same as that of the cleaning liquid in the reservoir.
Over time and with use, the filters used to remove residual material from the cleaning liquid may get plugged causing incremental flow reduction through the filtration system as well as to the cleaning station. As the flow through the filtration system decreases, the quality of the cleaning liquid in the reservoir is diminished and the temperature of the reservoir increases. Typically, an increase in the reservoir temperature above a pre-defined threshold is used as an indication to replace the filters.
U.S. Pat. No. 7,010,259 entitled “Apparatus and Method for Cleaning an Image Transfer Device” assigned to Hewlett-Packard Development Company, LP., the contents of which are hereby incorporated by reference in its entirety, describes a printer with two cleaning stations each associated with a tank for supplying cleaning liquid to one cleaning station and for receiving cleaning liquid with residual material from that cleaning station. Cleaning oil for both tanks is replenished by adding new liquid to one of the tanks and providing liquid communication between the tanks. As the volume of the tank that is not directly replenished with new liquid decreases it is replenished with liquid from the tank that is directly replenished with clean liquid. Although, the liquid is replenished, both tanks include a combination of clean and polluted liquid.
U.S. Pat. No. 6,343,610 entitled Method and Apparatus for Recycling Coolant for a Cutting Machine, assigned to Masco Corporation of Indiana, the contents of which are hereby incorporated by reference in its entirety, describes a skimming operation and a method of separating degreasing solution from the coolant mixture for recycling in the degreasing system. The skimmer includes a tank with a main chamber, an intermediate chamber and a collector. The used aqueous dispensing solution is collected by overflow into the collector from which it is delivered to an associated dirty coolant tank for use as feedstock in the coolant solution.
International Patent Publication No. WO09904907, entitled Ultrasonic Atomizing Device with Liquid Circulating Line, assigned to Green Clouds LTD, the contents of which are hereby incorporated by reference in its entirely, describes an ultrasonic device for atomizing liquids including at least one atomization unit containing a liquid to be atomized, a means for circulating the liquids to be atomized through a reservoir across each transducer and back to the reservoir. Overflow liquid from the unit carries both the floating type impurities and those settling type impurities which have been carried this far in the flowing liquid's current. This overflow liquid completes the circulation by returning to the reservoir. Thus impurities tend to concentrate in the reservoir rather than in the unit or on the transducer.
U.S. Pat. No. 4,964,987 entitled Cross Flow Filter Apparatus, filed Jun. 10, 1988, the contents of which are hereby incorporated by reference in its entirety, describes a cross flow filter apparatus and method that uses an open tank having a first liquid retaining section, a second filter retaining section and a third solids collecting section in fluid communication with each other. The floating contaminant removal means can comprise an overflow trough configuration disposed adjacent the top edge of the tank having a fluid outlet for removal of the floating contaminants which overflow into the solids collection section.